Well Water Testing

Well Water Testing

On a hot summer day nothing quite quenches your thirst better than a tall, cold, glass of ice water. As refreshing as that water may be and even though that glass of water may appear clean, the only sure way of knowing if your drinking water supply is safe to drink is to have your water tested.

The Story County Environmental Health Department offers free wellhead inspection and water testing for private water supply wells within Story County. During these inspections, the wellhead is checked for faults, which would compromise the water quality, such as a cracked casing, insufficient clearance of the casing above grade, improper seal or cap, and nearby abandoned wells. We also look at the area around the well to insure that there is not improper storage of chemicals and fertilizers which could compromise water quality and check for cross connections (connections in which water can flow between water sources and causing a safe water source to be contaminated from a unsafe water source). Finally, a water sample is collected from a sample tap at the pressure tank (untreated water) and sent to a certified lab to test for total coliform bacteria and nitrate level.

Coliform bacteria are a group of naturally occurring bacteria that are present throughout the environment. The presence of coliform bacteria in your well water indicates that a pathway exists that has allowed contamination of the well. The pathway may be caused by surface water run off, structural defects in the well or distribution system, repairs without proper disinfection, or groundwater contamination.

Nitrogen is an element that occurs naturally in the environment and all sources of nitrogen are sources of nitrate. There is a potential health risk to infants under one year of age and pregnant or nursing mothers when drinking water containing elevated amounts of nitrates. These risks occur because high nitrates can reduce the oxygen carrying capacity of the blood and cause "blue-baby" syndrome (or methemoglobinemia).

Nitrate concentrations exceeding the infant health advisory level of 45 mg/l (as NO3) are generally an indication of contamination from major nitrogen sources such as a sewage disposal system, animal manure, or nitrogen fertilizers. In the Story County area, nitrate contamination is more likely to occur in shallow wells or in wells that are poorly located, constructed, or maintained.

To be considered safe, your drinking water test results should show an absence of bacteria, and nitrate levels below 45 mg/L NO3 (below 10 mg/L if reported as N). If no bacteria is detected in the sample, but the nitrate level is greater than the MCL (maximum contaminant level), the well water will be re-sampled and tested for pesticides.

The Story County Environmental Health Department recommends annual testing for all wells, especially wells supplying drinking water. Sampling is conducted Monday through Wednesday. Please contact Environmental Health at 515-382-7240 to schedule an appointment.

If your recent private water supply well test was returned with a report that stated your water was "unsafe" with elevated levels of bacteria, you will need to contact a private well contractor and arrange to have a shock chlorination performed on your well and water system. Ten days after the chlorination has taken place, we may resample your well water to determine if the bacteria problem was eliminated with the chlorination. If your recent private water supply well test was returned with a report that stated you water was "unsafe" with elevated levels of nitrate or nitrogen, you will need to contact a private water supply well contractor to determine if structural defects within the well zone is the source of the nitrate/nitrogen problem in your water. To learn more about chlorination of private water supply wells, please follow this Well Chlorination link.